This invention relates generally to injection molding and more particularly to a valve gated injection molding system or apparatus having a heated valve member which is reciprocated by associated actuating mechanism.
As is well known, the thermal characteristics in the area of the gate of an injection molding system are critical to successful operation. In valve gating some materials, it has been found that the existing apparatus does not provide clean cosmetic gating because the forward tip end of the valve pin or member does not fully seat in the gate in the cooled mold. As shown in the applicant's U.S. Pat. Nos. 4,125,352 which issued Nov. 14, 1978 and 4,406,609 which issued Sep. 27, 1983, early attempts were made to overcome this problem by making the valve pins highly conductive to provide more heat at the forward tip end. While these arrangements are satisfactory for some applications, they have the disadvantages that the amount of heat which can be conducted to the forward tip end is limited and they are difficult to manufacture.
It is also well known to provide various stationary components of injection molding systems with integral electrical heating elements. Examples of this are seen in the applicant's U.S. Pat. Nos. 4,376,244 which issued Mar. 8, 1983, 4,820,147 which issued Apr. 11, 1989, 4,865,535 which issued Sep. 12, 1989 and the applicant's Canadian patent application serial no. filed Dec. 19, 1990 entitled "Injection Molding Probe with Varying Heat Profile." However, these previous systems do not have the problem of requiring reliable simultaneous provision of electrical power to numerous valve pins, each of which is reciprocating in a different stationary nozzle in the mold.